1. Field of the Invention
The present invention relates to a hydrogen gas station, a fuel cell system, and a hydrogen gas rate accounting device. More particularly, the present invention relates to a fuel cell system comprising a hydrogen gas station configured to generate a hydrogen-rich reformed gas through reforming reaction of an organic compound, and a plurality of fuel cells configured to consume the reformed gas to generate electric power.
2. Description of the Related Art
A fuel cell configured to generate electric power and heat from hydrogen as a fuel is capable of converting fuel energy into effective electric energy and heat energy with high conversion efficiency. For this reason, a fuel cell system is capable of inhibiting the amount of emission of carbon dioxide because of the high conversion efficiency, and is therefore expected to reduce the carbon dioxide which may be a cause of global warming.
In actuality, however, infrastructures of the supply system of hydrogen used as the fuel for the fuel cell are not adequately equipped. The fuel cell is typically equipped with a reformer capable of generating hydrogen from a feed gas supplied from the existing infrastructure, such as a city gas (see Japanese Laid-Open Patent Application Publication No. Hei. 07-57756 (first prior art)).
In addition, for the purpose of stable and efficient supply of hydrogen, a technology has been developed, in which a feed gas capable of being easily separated into hydrogen is equipped as an infrastructure, and the separated feed gas is recovered and re-used (see Japanese Laid-Open Patent Application Publication No. 2002-274801 (second prior art)).
Further, as a system for supplying hydrogen to areas, there has been proposed a hydrogen supply system including a reformer, hydrogen consumption equipment and hydrogen storage means which are networked. In this system, hydrogen can be supplied to the hydrogen consumption equipment sufficiently and efficiently (see Japanese Laid-Open Patent Application Publication No. 2002-372199 (third prior art)).
Assuming that the fuel cell system of the first prior art is employed as, for example, a home fuel cell system, the operation of the reformer equipped in the fuel cell is controlled to generate hydrogen in varying amount according to constantly varying amount of electric power or heat which the fuel cell is required to generate.
Typically, the reforming reaction (endothermic reaction) for generating hydrogen in the reformer is carried out at a high temperature of approximately 700° C. The change of operating conditions (e.g., temperature) of the reformer depending on the constant variation in the amount of hydrogen required causes a substantial heat loss, thereby resulting in reduction of hydrogen generation efficiency in the reformer. For example, if the temperature of the reformer is lowered to a room temperature and then increased up to 700° C., such a temperature increasing operation may cause substantial start energy loss and time loss.
In other words, the fuel cell system of the first prior art is undesirable to the home fuel cell system which is required to constantly vary the amount of electric power, because of difficulty in improving energy utilization efficiency of the reformer equipped in the fuel cell system.
In contrast to the fuel cell system of the first prior art, due to the use of the feed gas capable of being easily separated into hydrogen, the hydrogen storage and supply system of the second prior art is capable of dealing with a load fluctuation in electric power at home, although it is necessary to recover the feed gas from which hydrogen has been removed.
In the hydrogen supply system of the third prior art, the reformer, a number of hydrogen consumption equipment (e.g., fuel cells), and the hydrogen storage means are interconnected and networked to allow hydrogen communication. In this system, the variation in demands for hydrogen among this hydrogen consumption equipment can be mutually offset, and the demands for hydrogen are equalized in the entire fuel cell system. As a result, the amounts of gases supplied to this hydrogen consumption equipment are equalized. So, the hydrogen supply system of the third prior art is expected to resolve a problem of reduction of the hydrogen generation efficiency which may take place in the fuel cell system of the first prior art by keeping the operating conditions of the reformer.
By the way, part of hydrogen supplied to an anode of the fuel cell through a fuel gas inlet of the fuel cell is not consumed in the anode and is exhausted as an off gas from a fuel gas outlet of the fuel cell together with steam or carbon dioxide. The exhausted off gas has predetermined heat energy and is hence useful as a heat source. The efficient use of the off gas has been desired for the purpose of improvement of energy efficiency of the entire fuel cell system.
However, the efficient use of the off gas exhausted from the anode of the fuel cell and its recovery method are not achieved in the hydrogen supply system of the third prior art.
In addition, in the fuel cell system of the second prior art, recovery of the off gas using hydrogen absorbing alloy is suggested, but the efficient use of the off gas is not achieved as in the hydrogen supply system of the third prior art.